Arrays of light emitting devices, such as inorganic light emitting diodes, organic light emitting diodes or electroluminescent devices, etc., are becoming increasingly popular in displays. This popularity is chiefly due to the low operating voltages and power required and to the small size, as well as the ease of manufacturing. This is especially true of organic electroluminescent devices (OEDs), since manufacturing is even easier than many other light emitting devices, the brightness is even greater, and the voltage requirements are substantially less.
The problem is that most of the light emitting devices have an internal capacitance which charges during operation and remains charged after activation of the device. This lingering or persisting charge produces what is commonly referred to as shadows in the display, because the charge remaining from a previous row of data will continue to produce light emissions that appear in the next row of data and, in some circuits, may effect the next row of data. Because OEDs include a layer of organic material, which is nearly a dielectric, sandwiched between layers of conducting material, the internal capacitance is relatively large. Thus the shadow problem is especially prevalent in arrays of OEDs.
Accordingly, it would be highly desirable to produce an array of light emitting diodes in which no shadow is prevalent.
It is a purpose of the present invention to provide a new and improved array of light emitting devices with active pull down shadow canceling.
It is another purpose of the present invention to provide a new and improved array of light emitting devices with active pull down shadow canceling which adds very little complexity to the array.
It is still another purpose of the present invention to provide a new and improved array of light emitting devices with active pull down shadow canceling which is relatively simple and inexpensive to manufacture.
It is a further purpose of the present invention to provide a new and improved array of light emitting devices with active pull down shadow canceling in which the drivers are simplified and, thereby, cost is reduced.
It is a still further purpose of the present invention to provide a new and improved array of light emitting devices with active pull down shadow canceling which is easily integrated on a common substrate with little additional cost and effort.